The invention relates more particularly to the multiplexing devices associated with coding devices and the interaction between these devices.
The invention applies mainly to the control of a coding device by a multiplexer, and more particularly to the coding of video data.
Specifically, in coding systems including both a coding device and a multiplexing device, each of the devices possessing its own reference clock, it is difficult for a multiplexer to inform a coding device of the time at which it desires to receive a packet from the coding device, since it does not know the local time of the coding device. This is all the more noteworthy when the two devices are remote and the time of transit through the network separating the two devices is not constant but merely bounded.
The invention applies also to statistical multiplexing. Actually, very often the multiplexers of streams of MPEG-2 type for example are responsible for transmitting control cues, for controlling bit rate for example, to the various coding devices. However, these coding devices are not mutually synchronized and it is therefore difficult for a multiplexer to act simultaneously on these coding devices in order that they act at precise instants and that above all their action is received at a precise instant at the level of the multiplexer. The problem is all the more considerable when the coding devices are remote from the multiplexing device or devices since in addition to the asynchronism of the coding devices, the transit time through the networks linking them to the multiplexer is different in each network. The transit time may also vary with each establishment of a new connection through the network.
The known devices implement solutions allowing mutual synchronization between the various coding devices with the multiplexer.
Such solutions are complex to implement, uncompetitive and exhibit a considerable convergence time.
The invention proposes a multiplexing device which does not attempt to mutually synchronize the various coding devices but which circumvents such synchronization while making it possible to work with the various coding devices and to obtain synchronous actions at the input of the multiplexer.